Chytridiomycosis

The chytridiomycosis is a fungal disease ( mycosis ) in amphibians. Pathogens are the chytrid fungus ( Batrachochytrium dendrobatidis ) and Batrachochytrium salam andri vorans. The end of 1998 it was first discussed in the context of the global amphibian extinction crisis (Global Amphibian Decline ), as mono-causal cause this is controversial.

Pathogenesis

The pathogenesis is not fully understood. Probably there is a strong impairment of the biological functions of the outer skin of the gas, liquid and mineral metabolism as well as the production and release of skin secretions, so that the protection is no longer provided.

The development of the sporangia is a sign of the maturation of the virus. Through a hyperplastic response due to increased turnover of epidermal cells and premature keratinization and death of infected cells hyperkeratosis may occur.

As for favoring a Chytridiomycetes infection impairment of the immune system by various, mostly environmental stress factors or primary disease is considered. This could include:

• Non-optimal climatic and environmental conditions ( humidity, fresh air, temperature, light quality and light quantity)
• Stress by rapid climatic changes
• Unbalanced and one-sided diet
• Stress caused by an incorrectly assembled community in the terrarium
• Sudden transition from dry season to rainy season
• Sudden changes in the habitat of the frog, such as a modification of the facility or a reaction of the animal.
• Stress for the animal, for example, not properly transport, malnutrition, etc.
• Primary disease (eg worms, pseudomonas, etc.)

Occurrence

The disease probably originates from Africa and could be retrospectively found in the other clawed frog specimen from 1938. The chytridiomycosis was then a stable endemic in South Africa and was probably spread by trade in clawed frogs worldwide.

After the pathogen has become known in wild and held in captivity amphibians in Australia, North, Central and South America, infections are first described, which have been demonstrated in terrarium animals in Germany and the Netherlands. Imported poison dart frogs ( D. auratus, D. pumilio ) from Costa Rica Phyllobates vittatus and from French Guiana died due to chytridiomycosis within one week after arrival in Europe. Batrachochytrium was also isolated in frogs that have been proven in terrariums offspring ( Germany, Belgium ) were obtained. Due to the infestation and disease of animals that originated from proven terrariums offspring, still stands to reason that the pathogen of amphibians that are kept in captivity, latent is ubiquitous. Low amounts of infectivity could be detected even in healthy frogs and tadpoles, without leading to the outbreak of disease.

Also, in almost all species of amphibians in Europe the pathogen has now been proven. Studies between 2003 and 2010 revealed a prevalence rate of 7.5 percent at around 3000 individuals tested in Germany. Unlike in Australia and America, the infection in European amphibians seems but only relatively rarely erupt and usually take no dramatic course.

The type of fungus Batrachochytrium salam andri vorans attacks in north-west Europe - primarily in the Netherlands - Fire Salamander, which are affected by in their skin toxins. In the Netherlands, there was a stock slump of up to 96 % since 2010. The fungal infection often leads after seven days of the death of amphibians.

Symptoms

The chytridiomycosis manifests itself in lack of appetite to refusal to eat, apathy, impaired movement, ataxia, prolonged stay in the water and finally the death of the animal.

Lesions occur only in a subset of cases. The skin will appear dull, red, with whitish deposits and darkening of the skin color and the drawing pattern.

Diagnostics

The pathogen is very easy after the time of death and on the basis of biopsies, in this case, histological examination is performed after hematoxylin- eosin staining.

More difficult is the diagnosis after set-off or Abkratzproben by PCR. This provided proof with massive infestation is particularly possible. The report should in this case but only as positive if at the same sporangia are detected.

Meanwhile, an accurate method was developed to detect the fungus, both qualitatively and quantitatively by real- time PCR.

Therapy

Sick or infection endangered animals with antifungal eg itraconazole treat than 10 minute bath daily for 7-10 days. Terrariums must be thoroughly cleaned and disinfected (eg with benzalkonium chloride or other fungicidal disinfectants, heat, dryness, or 70 % ethanol).

Also has chloramphenicol, a broad spectrum antibiotic, proved to be an effective means of therapy itself heavily infested animals, such as New Zealand scientists were able to demonstrate in studies on Litoria ewingii and L. raniformis.

Batrachochytrium dendrobatitis survives no dehydration. To prevent the spread of this fungus to be fitted with water coming into contact material, such as water sports or fishing tackle, to be completely dried. Likewise, the trade in animals and plants from the waters concerned and their unwanted movement and following contact with local fauna is a great risk for B. dendrobatitis - free regions and their amphibians dar.